Low temperature heat source usually refers to heat sources below 200° C. There are a variety and the huge amount of low temperature heat sources, including solar energy, geothermal energy and industrial waste heat. According to statistics, the solar radiation of two-thirds of the whole land area in China is greater than 5000 MJ per square meter. The geothermal energy in China can be equal to about 3.3 billion tons of standard coal. Since the low-temperature heat sources featured with a wide distribution and low quality it is difficult to be utilized by conventional energy conversion devices, resulting in that most of these energy vain discharged into the environment causing great waste and environmental pollution. Therefore, the exploration of technologies for rationally using these low temperature heat sources becomes such a hot topic in the field of energy technology. Organic working fluid power generation and ejector refrigeration system using organic working fluid is considered the most potential technology for the utilization of low temperature heat sources, which has a wide range of options, suitable cycle and high energy efficiency compared with the water vapor, when the heat source temperature is below 270° C.
The ejector refrigeration system appeared in the early 20th century, and there have been some applications. However, due to its low efficiency, bulky equipment and other reasons, it is gradually replaced by compact and more efficient compression refrigeration system. In recent years, however, the ejector refrigeration system again becomes a research focus in the field and attracts widespread concern. The ejector refrigeration system has several advantages. It does not contain moving parts and has a simple structure, reliable performance, easy maintenance, etc. The operating parameters of the refrigerant system are more suitable for low temperature heat sources such as solar energy, geothermal energy and industrial waste heat.
After searching for the existing literature, Huang B. J. et al published an article entitled “A solar ejector cooling system using refrigerant R141b” (B J Huang, J M. Chang “A solar ejector cooling system using refrigerant R141b.” Solar Energy, 1998 (64)1223-226). This paper presents a new ejector refrigeration system program, which uses a high-performance ejector refrigeration unit with heat recovery. One-dimensional mathematical model of ejector proposed by previous researchers was improved, and the ejector refrigeration performance of the system was calculated to obtain a good cooling effect. Zheng Bin et al published an article entitled “A combined power and ejector refrigeration cycle for low temperature heat sources” (Zheng Bin, Y W Weng. “A combined power and ejector refrigeration cycle for low temperature heat sources” Solar Energy, 2010 (84): 784-791). The combined cycle will adopt expander and ejector, improving the efficiency of using the low temperature waste heat sources according to the energy cascade principle. The system uses latent heat of vaporization working fluid for cooling and improves performance of cooling and power generation system. Currently, the similar ejector refrigeration system for low temperature heat source has been extensively studied. The researches focus primarily on mathematical modeling, optimization of the ejector, and the ejector's experimental performance.
The traditional method of cooling has to work with external power. It needs pump to provide pressurized working fluid which consumes a lot of power. In addition, the control process also requires an external power supply, resulting in reduced overall system efficiency and increasing construction and maintenance costs.